The use of surface treatment of plastic substrates to enhance the bond and product assurance of laminates produced by bonding said treated substrates with a polyurethane adhesive has been the general practice for a decade or more in the automobile industry but recently the industry has required the laminates to withstand heating above 375.degree. F. (190.degree. C.) and trouble has been experienced with the usual laminates due to bond failure, generally at the adhesive substrate interface. It should be noted this effect has been observed with surface primers and paints as heat causes bubbles, pits and related effects. Particularly this is true with the polyester fiber glass impregnated substrates, those most popular being the so-called "low profile" molded polyesters which contain agents such as waxes, block polymers and polyolefins to reduce shrinkage of the plastic from the glass fibers. These polyesters have been discovered to evolve vapors such as styrene, water, and carbon dioxide and other gases at 190.degree. C. for a short time.